CCNA Exam Notes: Cisco Certified Network Associate

CCNA Exam Notes: Cisco Certified Network Associate

by Todd Lammle
     
 

The CCIE (Cisco Certified Internetworking Expert) certification denotes proficiency in supporting diverse Internetworks that use routing and bridging technologies. This text provides coverage of the CCNA exam including exactly what the candidate needs to know to pass the exam. See more details below

Overview

The CCIE (Cisco Certified Internetworking Expert) certification denotes proficiency in supporting diverse Internetworks that use routing and bridging technologies. This text provides coverage of the CCNA exam including exactly what the candidate needs to know to pass the exam.

Product Details

ISBN-13:
9780782125351
Publisher:
Wiley, John & Sons, Incorporated
Publication date:
03/01/1999
Series:
CCNA Exam Notes Ser.
Edition description:
Older Edition
Pages:
352
Product dimensions:
5.85(w) x 8.21(h) x 0.97(d)

Related Subjects

Read an Excerpt


Chapter 2: WAN Protocols

...Identify ISDN protocols, function groups, reference points, and channels

People in the networking industry tend to use a lot of acronyms and other lingo to describe basic things. The parts of ISDN are no exception. In this section, we define some of these terms and the features they describe.

The components we describe are really the nuts and bolts of ISDN, which are very important for you to understand both when you are setting up an ISDN connection and studying for the CCNA exam.


Critical Information

This section focuses on ISDN and how Cisco views its protocols, function groups, reference points, and channels.

ISDN Protocols

ISDN protocols are defined by the ITU-T. Here are three diverse ISDN protocols whose function is specified by their first letter:

  • E protocols apply to ISDN on an existing telephone network.
  • I protocols deal with concepts, terminology, and services.
  • Q protocols pertain to switching and signaling.

Function Groups

Function groups connecting to the ISDN network are known as terminals. These come in two types:

  • TE1 (Terminal Endpoint Device type 1) is a BRI (Basic Rate Interface) that understands ISDN standards. (BRI will be covered in detail in the next section of this chapter.)

  • TE2 (Terminal Endpoint Device type 2) predates ISDN standards. To use a TE2, you have to use a terminal adapter (TA) to generate BRI signals for a Cisco router interface.

ISDN Reference Points

ISDN uses four different reference points to define logical interfaces between functional groupings such as TAs and NT1s. They are as follows:

  • R defines the reference point between non-ISDN equipment and a TA.
  • S defines the reference point between user terminals and an NT2.
  • T defines the reference point between NT1 and NT2 devices.
  • U defines the reference point between NT1 devices and line-termination equipment in a carrier network. (This type of reference point is only used in North America where the NT1 function isn't provided by the carrier network.)

ISDN Channels

There are two types of channels used in BRI ISDN: B and D. Here's what each one does:

  • B, or bearer, channels have a 64Kbps capacity. They can be used for voice or data. Two B channels in a BRI can be combined for a total of 128Kbps.
  • D, or data, channels are used for call signaling or clocking. This type of channel has a 16Kbps capacity.

NOTE     To learn more about ISDN and channels, read the Sybex Advanced Cisco Router Configuration (ACRC) Study Guide.


Exam Essentials

To pass this portion of the exam, you'll need to remember the terminology used for ISDN features, as well as how the various parts function.

Understand the different protocols used in ISDN. The Q protocol specifies switching and signaling. E protocols apply to ISDN on an existing telephone network. I protocols deal with concepts, terminology, and services.

Know the difference between a B channel and a D channel. A BRI uses 2 B channels and one D channel. Each B channel is 64Kbps; a D channel is 16Kbps.


Key Terms and Concepts

BRI: Basic Rate Interface (BRI) is an ISDN interface composed of two B channels and one D channel for circuit-switched communication of voice, video, and data.

ISDN: A digital communication protocol that permits telephone networks to carry data and voice transmissions at higher speeds than typical analog transmission rates.

ITU-T: International Telecommunication Union Telecommunication Standardization Sector. This group creates international standards for internetworks and telecommunications.

OSI: An acronym for Open Systems Interconnection, OSI was created by the International Organization for Standardization (ISO) to create a layered approach to interoperability between disparate systems.

Reference Point: Used to define logical interfaces in ISDN.


Sample Questions

1. What does an R reference point define?

A. The reference point between non-ISDN equipment and a TA
B. The reference point between ISDN equipment and a BRI
C. The reference point between ISDN equipment and a PRI
D. The reference point between non-ISDN equipment and an NA1

Answer: A. R reference points are used when connecting ISDN to a router interface other than a BRI or PRI.

2. When protocols begin with the letter Q, what does that specify?

A. Switching and signaling
B. Existing telephone service
C. Concepts, terminology, and services
D. Quality ISDN service

Answer: A. To read about switching and signaling in ISDN, look for the specifications and protocols that begin with Q.
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